Five siblings have been jailed for more than three years for illegally extracting water from an aqueduct feeding a Unesco-listed Spanish nature reserve that is threatened by desertification, a court ruling showed. The farmers – four men and a woman – were found guilty of crimes against the environment and causing damage through the “systematic and extensive extraction” of water supplying Donana national park, according to the ruling dated 18 September that was seen by Agence France-Presse on Friday. One of Europe’s largest fauna-rich wetlands, Donana is located in the southern Andalusia region. If confirmed by a higher court, it would be the first ruling to involve a jail sentence for illegally tapping water from Donana, a site that has become a symbol of the growing scarcity of water in Spain which is causing fierce political debate, El Pais newspaper said. The siblings were found guilty of extracting 19m cubic litres of water for their Hato Blanco Viejo ranch between 2008 and 2013, leaving the groundwater reserves in “poor condition” and causing permanent lagoons to become seasonal due to the lower water levels, it said. The defendants, who have been given more than a dozen fines for water-related issues since the last 1990s, must also pay €2m (£1.74m) in compensation to the Guadalquivir Water Authority, the public body responsible for local water management. They have been banned from cultivating crops for two years. Donana, a diverse ecosystem of lagoons, marshes, forests and dunes that stretches across 100,000 hectares, is on the annual migratory route of millions of birds and is home to many rare species, such as the Iberian lynx. The park has been struggling due to an ongoing drought and is threatened by intensive agriculture in the area. Despite warnings from Unesco and the European Commission, Andalusia’s right-wing regional government is pushing to extend irrigation rights near the park, with a draft law seeking to regularise berry farms that are irrigated by illegal wells. The bill will be put to a vote in the coming weeks and if it passes, environmental groups say it could legitimise 1,500ha (3,700 acres) of crops and jeopardise the future of the reserve. In that instance, Spain’s left-wing government has pledged to appeal while Unesco has said the park could lose its status as a protected world heritage site. The draft bill played a key role in political campaigning ahead of local polls in May and a general election in July in a country where 80% of water resources are used in agriculture. Spain is the world’s biggest exporter of olive oil and the European Union’s biggest producer of fruit and vegetables.